An electronic device, such as an embedded device, is generally provided with an internal clock unit, for example, a Real Time Clock (RTC) unit. The RTC is a machine clock (most often in the form of an integrated circuit) that keeps track of the current time. Although the term often refers to the units in personal computers, servers and embedded systems, RTCs are present in almost any electronic device which needs to keep accurate time, such as a digital camera, a Personal Digital Assistance (PDA), a mobile phone, a home appliance and the like. RTCs often have an alternate source of power, so they can continue to keep time while the primary source of power is off or unavailable.
In many electronic devices, a system time is needed for a time displaying function or for running time-sensitive applications, for example, applications updating a virus library of anti-virus software. The time read from the RTC is usually utilized as the system time of the electronic devices.